Dear Members of the dc-international mailing list,
Many of you will be at the Seventh DC workshop next week in
Frankfurt [1]. There has been alot of discussion over the past few
weeks in the DC Advisory Committee in support of the registry
design and goals that the Working Group for DC in Multiple
Languages has long advocated [2].
Over the past year, the Dublin Core Metadata Initiative has focused
largely on the revision and ratification of the basic element set. As
of October 1999, the two main building blocks for a distributed
registry of Dublin Core (in Multiple Languages) are finally in place:
Version 1.1 of the Dublin Core [3] has been finalized, and RDF Schema
Proposed Recommendation [4] is close to ratification.
You may recall that the DC-ML working group decided to set up a
distributed registry of Dublin Core multiple languages based on RDF
schemas. The registry would initially cover only the fifteen elements;
eventually, a process would be needed for extending the scope of the
registry to qualifiers as they became ratified by the Dublin Core
community. Thomas Baker and Xu Bo developed an initial Java prototype
of this RDF schema registry at AIT in Thailand. They then passed the
code to Mitsuharu Nagamoto, Shigeo Sugimoto, Tetsuo Sakaguchi, and
Koichi Tabata at ULIS in Japan, who have reimplemented the basic
registry first in C, then in Java [5, 6]. This prototype currently
provides RDF schemas of Dublin Core in various languages (fourteen as
of 20 September 1999), with an interface for selecting and correctly
displaying the Dublin Core schemas in their proper fonts (using the
ULIS-developed "MHTML" applet for handling the display of non-Latin
fonts). The prototype holds all of these schemas on the local server;
by design, however, these schemas would be distributed over the Web to
servers in places like Helsinki and Bangkok.
The Advisory Committee is currently discussing a more general proposal
(see below), which would institute a process for proposing and vetting
qualifiers for adoption as Recommended Interoperability Qualifiers.
In Frankfurt, a meeting has been scheduled for the Working Group for DC
in Multiple Languages on Tuesday afternoon. By this time, the Advisory
Committee will have met and hopefully approved a version of the
proposal below. Likewise, the Datamodel and Schema (Interoperability)
Working Groups will have met and discussed the technical aspects of this
registry project.
The goal of our DC-ML meeting on Tuesday should be to assess the registry
and related processes from the point of view of Dublin Core in multiple
languages. Aspects of this question include: ground rules for participation
in the qualifier approval process; management of namespaces; "authorized"
or "endorsed" versions of Dublin Core; schema maintenance.
By the end of next week, I would like to work out the precise scope of
our Tuesday October 26 with all of you, especially those who will be
attending DC-7. The floor is open for comments and discussion. I look
forward to seeing many of you in Frankfurt.
Cheers,
Tom
[1] http://www.ddb.de/partner/dc7conference/index.htm
[2] http://purl.org/DC/documents/working_drafts/wd-multilingual-current.htm
[3] http://purl.org/dc/elements/1.1
[4] http://www.w3.org/TR/WD-rdf-schema
[5] http://mhtml.ulis.ac.jp/~nagamori/DCML/
[6] http://avalon.ulis.ac.jp:8080/~nagamori/
------------------------------------------------------------------------
This document:
1999-10-01 Posted by Tom Baker and Stuart Weibel
http://www.mailbase.ac.uk/lists/dc-ac/1999-10/0005.html
Title: "Process for Qualifiers: A Proposal"
1999-10-08 This version, corrected by Tom Baker in light of the
reactions (summarized at
http://www.mailbase.ac.uk/lists/dc-ac/1999-10/00xx.html).
------------------------------------------------------------------------
A Registry for Dublin Core Elements and Qualifiers
1. Premise
Implementers of Dublin Core elements often need to customize these
broad, generic elements in order to meet specific local
requirements. To support this, the Dublin Core Metadata Initiative
(DCMI) has defined standard ways to "qualify" elements with various
types of qualifiers. However, an uncontrolled proliferation of
local qualifiers in domain-specific applications and in
non-English-language adaptations of Dublin Core elements threatens
to compromise semantic interoperability among Dublin-Core-based
applications and schemas. This proposals presents guidelines and
basic principles for a registry of Dublin Core elements and
qualifiers along with a process for publicizing ("registering")
local qualifier usage and proposing qualifiers of general interest
for recognition as Recommended Interoperability Qualifiers of the
DCMI. This registry will initially be implemented
as a distributed database in the RDF Schema format [2].
2. Purposes of the registry
2.1. Providing a context for the formal management of a
metadata namespace by the DCMI.
2.2. Making qualifiers used in DC-based projects, whether or
not they are officially recommended by DCMI, visible to users,
schema designers, metadata implementers, and DCMI usage
reviewers.
2.3. Promoting the use of qualifiers that meet DCMI guidelines
and have been found to be useful across disciplines or
languages.
2.4. Making Dublin Core elements and qualifiers available in
a machine-readable form for automatic processing by metadata
applications.
3. Guidelines for Dublin Core Interoperability Qualifiers
According to the DCMI Data Model Working Group, there are three types
of Dublin Core qualifiers [1]. In order to fulfill the formal
requirements of a Dublin Core Interoperability Qualifier, these
qualifiers must meet specific criteria:
3.1. Element Qualifiers
3.1.1. Element Qualifiers refine the semantics (ie,
narrow the definition) of a element. For example, an
"illustrator" (narrower) is a type of "creator"
(broader).
3.1.2. As recently as 1998, the Dublin Core community
referred to Element Qualifiers as "Types" or "Sub-Elements."
3.1.3. Element Qualifiers should follow the "dumb-down
principle," according to which a "dumb" client that
does not recognize a given element qualifier can simply
ignore that qualifier and yet still "understand" or use
the unqualified element value in some coherent manner.
3.2. Value Qualifiers
3.1.1. Value qualifiers are controlled terms that
specify how a value is encoded and may be parsed (for
example, "ISO8601" to make clear that "1999-04-12"
means April 12th and not December 4th) or provide a
context for the interpretation of a value (for example,
to specify that a number is a Dewey decimal
classification).
3.1.2. As recently as 1998, the Dublin Core community
referred to Value Qualifiers as "Schemes."
3.3. Value Components
[To be filled in, as indicated in my earlier posting.
Any volunteers?]
4. Qualifier registration and endorsement
4.1. Registered Qualifiers
4.1.1. Any qualifier in a Dublin-Core-based schema or
application may be "registered" in the Dublin Core
registry by making that qualifier or schema available
on the Web in RDF schema format and communicating its
Web address to the DCMI. To help users with the RDF
schema format, a Web form will be made available to
format a given schema automatically.
4.1.2. Registration provides a public record of
qualifiers in use by local projects and promotes the
reuse of qualifiers by others. However, registration
does not in itself imply that a given qualifier meets
DCMI guidelines or has been endorsed by the DCMI.
4.1.3. Each registered element and qualifier will have
a URI identifier plus a name and definition expressed
in any language (not necessarily English).
4.2. Proposed Interoperability Qualifiers
4.2.1. Any Registered Qualifier may be proposed for
promotion to the status of Proposed Interoperability
Qualifier by providing a name (label) and definition
(description) in clear and understandable English --
again, via a Web form.
4.2.2. A DCMI Usage Committee will evaluate the
proposed qualifier against the Guidelines for
Interoperability Qualifiers. Qualifiers judged by at
least two thirds of the Usage Committee to
substantially meet these formal guidelines will be
assigned a global interoperability token.
4.2.3. The DCMI Usage Committee will specify whether
Proposed Interoperability Qualifier is an Element
Qualifier, Value Qualifier, or Value Component.
4.3. Recommended Interoperability Qualifiers
4.3.1. Any Proposed Interoperability Qualifier may be
promoted to the status of Recommended Interoperability
Qualifier if it has been shown to be of general use and
broad interest across disciplines -- for example, by
adoption by five or more independent applications in three
or more domains or sectors.
4.3.2. Specialized, community-specific qualifiers
should be defined in separate namespaces; the DC
namespace should be reserved for qualifiers of general
interest across disciplines.
4.3.3. The DCMI Usage Committee may want to recommend
that multiple Proposed Interoperability Qualifiers of
similar scope be combined into one single Recommended
Interoperability Qualifier.
4.3.4. It will be hard to deprecate qualifiers once
they have been recommended, so the DCMI Usage Committee
should initially apply the qualifier guidelines
conservatively. Qualifiers that violate the formal
guidelines but are nevertheless in wide use should be
considered on a case-by-case basis. For the long term,
the DCMI should devise processes for revising
definitions and retiring or deprecating elements or
qualifiers in response to changing patterns of usage.
[1] http://www.ukoln.ac.uk/metadata/resources/dc/datamodel/WD-dc-rdf/
[2] http://www.w3.org/TR/WD-rdf-schema
_______________________________________________________________________________
Dr. Thomas Baker [log in to unmask]
GMD Library
Schloss Birlinghoven +49-2241-14-2352
53754 Sankt Augustin, Germany fax +49-2241-14-2619
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